A computer network is a collection of interconnected computing devices that exchange data and share resources. In a packet-based network the computing devices communicate data by dividing the data into small blocks called packets. Certain devices within the network, such as routers, maintain routing information that describes routes through the network. In this way, the packets may be individually routed across the network from a source device to a destination device. The destination device extracts the data from the packets and assembles the data into its original form. Dividing the data into packets enables the source device to resend only those individual packets that may be lost during transmission.
A virtual private local area network service (VPLS) may be used to extend two or more remote customer networks, i.e., VPLS sites, through a network (usually referred to as a provider network), such as the Internet, in a transparent manner, i.e., as if the network does not exist. In particular, the VPLS transports layer two (L2) communications, such as Ethernet packets, between customer networks via the network. In a typical configuration, routers coupled to the customer networks (such routers will be referred to as “members of the VPLS”) define label switched paths (LSPs) (also referred to as a pseudowire) within the provider network to carry encapsulated L2 communications as if these customer networks were directly attached to the same local area network (LAN).
In some cases, a VPLS may be supported across more than one autonomous system (AS) within a service provider (SP) network. Each AS may comprise an individual network including at least one border device that communicates with routers in other ASs. In this case, an inter-AS VPLS may be used to extend two or more remote customer networks through several independent networks as if the networks did not exist. Routers coupled to the customer networks define LSPs within each AS to carry encapsulated L2 communications. Border devices in each AS establish pseudowires (PWs) (i.e., LSPs to carry VPLS traffic) between the ASs to carry encapsulated L2 communications. PWs may emulate a L2 communication service, such as Ethernet, over the SP network.
In one case, for each inter-AS VPLS, a virtual local area network (VLAN) is manually established between the border devices in a first AS and a second AS to facilitate communication between the remote customer networks. However, this imposes a significant burden on both the control plane and the data plane of the border devices, which limits the number of inter-AS VPLSs that can be supported across the first AS and the second AS. In another case, for each inter-AS VPLS, the border devices automatically provision PWs between each of the routers in the first AS and the second AS that are members of the inter-AS VPLS to facilitate communication between the remote customer networks. In this way, if the inter-AS VPLS includes M routers in the first AS and N routers in the second AS, the border devices will automatically provision a full mesh of M*N PWs between the first AS and the second AS. However, if the inter-AS VPLS includes a large number of routers in the first AS and the second AS, the number of PWs established between the border devices of the first AS and the second AS will create scaling issues for the inter-AS VPLS.